Example of how to implement Fibonacci sequence in python

Introduction

Fibonacci sequence, also known as the golden section sequence, refers to such a sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21,... in Mathematically, the Fibonacci sequence is defined recursively as follows:

F(0)=0, F(1)=1, F(n)=F(n-1)+F(n -2) (n≥2, n∈N*).

1. Tuple implementation

fibs = [0, 1]
for i in range(8):
 fibs.append(fibs[-2] + fibs[-1])

This can get a list of Fibonacci numbers within the specified range.

2. Iterator implementation

class Fibs:
 def __init__(self):
  self.a = 0
  self.b = 1
 
 def next(self):
  self.a, self.b = self.b, self.a + self.b
  return self.a
 
 def __iter__(self):
  return self

This will get an infinite sequence, which can be accessed in the following way:

fibs = Fibs()
for f in fibs:
 if f > 1000:
  print f
  break
 else:
  print f

3. Implementation through custom class

class Fib(object):
 def __getitem__(self, n):
  if isinstance(n, int):
   a, b = 1, 1
   for x in range(n):
    a, b = b, a + b
   return a
  elif isinstance(n, slice):
   start = n.start
   stop = n.stop
   a, b = 1, 1
   L = []
   for x in range(stop):
    if x >= start:
     L.append(a)
    a, b = b, a + b
   return L
  else:
   raise TypeError("Fib indices must be integers")

In this way, you can get a data structure similar to a sequence, and you can access the data through subscripts:

f = Fib()
print f[0:5]
print f[:10]

4.Python implements a relatively simple Fibonacci sequence example

Put one first Take a look at the Fibonacci numbers...

0 1 1 2 3 5 8 13 21 34 55 89 144 233...

First assign values ​​to the first two variables:

i, j = 0, 1

Of course, you can also write it like this:

i = 0
j = 1

Then set a range, just It’s ready within 10000:

while i < 10000:

Then output i in the while statement and design the logic:

print i,
i, j = j, i+j

Need to pay attention here: "i, j = i, i+j" code It cannot be written as follows:

i = j
j = i+j

If it is written like this, j is not the value of the addition of the first two digits, but the value of the addition of i and j that have been assigned values ​​by j. In this case, the output sequence It will look like this:

0 1 2 4 8 16 32 64 128 256 512 1024 2048 4096 8192

The correct whole code looks like this:

i, j = 0, 1
while i < 10000:
 print i,
 i, j = j, i+j

Finally show the running results:

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765

Summary

The above is all about using Python to implement the Fibonacci sequence. I hope the content of this article can be of some help to everyone's study or work. If you have any questions, you can leave a message to communicate.

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